Add WebPrescientNetworking to trigger preconnect from Blink.

Source/core/core.gypi

 {
     'variables': {
         'core_idl_files': [
             'css/CSSCharsetRule.idl',
             'css/CSSFontFaceLoadEvent.idl',
             'css/CSSFontFaceRule.idl',
             'css/CSSHostRule.idl',
             'css/CSSImportRule.idl',
             'css/CSSMediaRule.idl',
             'css/CSSPageRule.idl',
@@ skipping 3037 matching lines @@
             'platform/network/HTTPHeaderMap.cpp',
             'platform/network/HTTPParsers.cpp',
             'platform/network/HTTPParsers.h',
             'platform/network/HTTPRequest.cpp',
             'platform/network/HTTPRequest.h',
             'platform/network/MIMEHeader.cpp',
             'platform/network/NetworkStateNotifier.cpp',
             'platform/network/NetworkStateNotifier.h',
             'platform/network/ParsedContentType.cpp',
             'platform/network/ParsedContentType.h',
+            'platform/network/Preconnect.h',
+            'platform/network/Preconnect.cpp',
             'platform/network/ProxyServer.cpp',
             'platform/network/ResourceError.cpp',
             'platform/network/ResourceError.h',
             'platform/network/ResourceHandle.cpp',
             'platform/network/ResourceHandleClient.cpp',
             'platform/network/ResourceHandleInternal.h',
             'platform/network/ResourceLoadTiming.cpp',
             'platform/network/ResourceRequest.cpp',
             'platform/network/ResourceRequest.h',
             'platform/network/ResourceResponse.cpp',
@@ skipping 611 matching lines @@
                 'bison_exe': 'bison',
                 # We specify a preprocess so it happens locally and won't get
                 # distributed to goma.
                 # FIXME: /usr/bin/gcc won't exist on OSX forever. We want to
                 # use /usr/bin/clang once we require Xcode 4.x.
                 'preprocessor': '--preprocessor "/usr/bin/gcc -E -P -x c++"'
               }],
          ],
     }
 }